According to many historians, fluid mechanics may be the oldest subfield in physics and engineering. In particular, ancient civilizations needed to control water flow for agricultural development, drinking-water supplies, and transportation. Thus, the development of fluid mechanics, which is the study of the motion and behavior of fluids, led to even more (and complex) improvements. For example, agricultural requirements led to irrigation waterways, dams, weirs, pumps, and even crude forms of “sprinkler systems”; the need for a potable (drinkable) water supply led to better wells, fountains, and water storage systems; and water transportation innovations included improved sails and rigs, as well as methods to build and waterproof sailing vessels.

To understand the way lava flows from a volcano, mathematicians apply their knowledge of fluid mechanics.

But early fluid mechanical studies did not end there. Over time, they extended into almost every realm of science and engineering. For example, mechanical engineering uses fluid mechanics because of the need to know about fluids used in combustion (ships and automobiles), lubrication (from the smaller inner workings of a wheel to larger mechanisms such as locks along a canal), and energy systems (hydroelectric power). Civil engineering utilizes fluid mechanical studies to interpret how fluid systems traveled over structures (aqueducts and pipes carrying drinking or waste water). Electrical engineers use fluid flow to analyze how to cool electronic devices with either air or water. Even early (and current) aeronautical engineers needed to know how air flowed over an airplane wing, providing the much-needed lift that allows a plane to become airborne.